they must be kept in place till the cement dries. This is effected by
means of many contrivances, regarding which the operator must employ
_some_ original inventiveness. Firstly, the pieces can often be simply
tied, or attached by pieces of tape, or parchment, or paper glued on.
In other cases india-rubber bands are useful. Again, bits of wood, or
sticks and wires, are the things useful. A bed of wax is generally a
sure guard. It is best to do this with great care, and not impatiently
rely on holding the pieces together with the fingers till they stick.
This is often the most difficult part of the whole operation; therefore
it should be done well and deliberately. And here it may be remarked
that, as in surgery, the most complicated cases of fracture may be
studied out and adjusted; for which reason I dare say that skilful
surgeons would be good menders of crockery, just as good astronomers
are always good riflemen.
When the broken pieces are adjusted and all is dry, there remain
the chips, hollows, ragged edges, and “hairs,” as the French call
them, or lines of juncture, to be filled and smoothed. This is done
with the cement which you employ, according to the quality of the
material, either plaster and gum-arabic, silicate and whiting, or
powdered chalk. Some experts succeed with white of an egg and finely
powdered quicklime, which holds firmly, but which requires practice to
amalgamate. Fill the cavities carefully, pressing the cement well in,
as the Romans did, with a stick or point. When all is smooth, paint
over the blank spaces and varnish with Sohnée, No. 3, or with a slight
coating of silicate. Fine copal varnish is rather tougher or less
brittle.
The most thorough process of all is to unite the fragments with a
vitreous or metallic _flux_, such as the silicate--there are several of
these--and then have the work baked or fired. It can then be painted
with porcelain colours under glaze, and fired again. As this is very
delicate, difficult, and expensive, few amateurs will care to try
it. It is, however, perfect, and by means of it the most complete
reparation can be effected. The Japanese do this simply with the
blow-pipe, by means of which they fix enamel powders even on wood. This
use of the pipe is also difficult, but the ancient Romans are said to
have employed the process with most minor work. As a thread of glass
will melt in a candle, and as fine-glass powder is equally fusible, it
can be understood that under the flame of a blow-pipe the latter can
often be melted so as to avail in restoration.
CROCKERY, OR FAÏENCE, AND PORCELAIN.--“Crockery,” by which we commonly
understand such ware as that of the blue willow plates, is far
superior to terra-cotta, since its _core_ or basis is thin, and very
hard, and its gloss of a different description, and more incorporated
with the body; or it is of a single superior body.
PORCELAIN differs entirely from the other two kinds of fictile ware,
being an elaborate mineralogical compound, its base being _kaolin_,
a friable, white, earthy substance, requiring great care in its
preparation, and _petunse_, or feldspar, which is united with the
_kaolin_. The result is a very delicate and beautiful diaphanous
ware, or one through which light passes to a limited degree. Both
crockery and porcelain are far more difficult to mend, owing to the
impossibility--particularly with the latter--of making fractures
disappear.
The first and most simple process of mending both kinds of ware is
to make small holes with a drill along the edges of the fracture,
and then, adjusting the fragments, bind them together with wire. M.
RIS-PAQUOT claims that “the honour of this discovery belongs properly
to a humble and modest workman named DELILLE, of the little village of
Montjoye, in Normandy.” But the archæologist will say of this claim,
as the English judge did of a similar one, that the plaintiff might as
well apply for a patent for having discovered the art of mixing brandy
with water, since there was probably never yet a savage who had wire,
or even string, who did not know enough to mend broken calabashes,
jars, and pipes by this solid method of sewing. From the time when
large earthen punch-bowls were first used in Europe, we find them
mended with silver wire. It is needless to devote whole pages with
illustrations, as M. RIS-PAQUOT has done, to show how to effect such
mending. The holes are made with either a bore or hand drill, such as
can be bought in every tool shop. If the reader will obtain one and
experiment with it on any penny plate or broken fragment, he will soon
master all the mystery. The wire is made fast by a turn with a pair of
nippers or pincers. Before fastening, wash the edges of the ware with
white of egg in which a very little whiting, or finely powdered lime or
plaster of Paris, has been mixed.
I may here observe that the wire for china-drilling should be half
round, or flat on one side. To prepare this, take brass wire, say a
length of about two feet, and, holding an old knife, draw the wire
firmly and steadily against it.
There are endless cements for sale by chemists, all warranted perfect,
to mend glass and china, and most of them do indeed answer the purpose
very well, for nature has given us not a few materials wherewith to
repair accidents. Thus, even boiling in milk will often suffice to
reunite broken edges. But I believe that of all, the Turkish cement
already described, which is made of gum MASTIC (a term improperly
applied in France to putty, by Americans to lime-plaster on houses, and
by Levantines to spirit with resin in it), is the most adhesive and
resistant to heat, cold, or moisture.
The art of mending does not consist so much of knowing what to use for
an ADHESIVE (since, as I have said, every chemist’s shop abounds in
these) as in skill and tact with which fragments are brought and kept
together, missing portions supplied, and in knowing the substance with
which to fill a blank. There are cases in which, when a hole has been
knocked in a china or glass plate, it can be drilled out round, and a
disc of the same substance or colour, or even of another, inserted.
This is almost an art by itself, and by means of it very singular and
puzzling effects may be introduced; as, for instance, when a number of
holes are drilled in a white china plate and then filled with discs
of coloured china, agate, coral, &c. In the East, turquoise and coral
beads are often thus set into porcelain, as well as wood. The mastic or
acidulated glue is used to make the objects inserted hold firmly.
As the smoker, when he breaks his pipe across the stem, has it repaired
with a short silver slide or tube, so when a china jar is broken across
the neck, the reparation can be concealed by a silver collar, which is
sometimes a great improvement; as, for instance, when the head of a
china dog, or even of a china man, is taken off. But in a great many
cases, or in all where this kind of concealment is advisable, it may
be made, like Cæsar’s wife, beyond suspicion, by making the collar or
concealing ornament, or leaf or flower, of silicate and whiting so as
to resemble the ware itself, which can be done very nicely.
SILICATE OF SODA is sometimes sold in the form of a dry solid, which is
placed in a little vinegar, and warmed. When dissolved it can be used
_ad libitum_. It is often used as a glaze for stone.
There is a curious old story about mending broken crockery by means of
magic--or rather by deceit--which, though not of a practical nature, is
at least amusing. It is partially told in a book published about 1670,
entitled _Joco-Seriorum Naturæ et Artis Magiæ Naturales Centuriæ Tres_.
It happened once in Mergentheim that there was a great fair, when the
whole courtyard of the palace was full of earthenware vessels for sale
_ab assidentibus muliebibus_ (by attendant women). Seeing this, the
Prince of Mergentheim went about among these women, and so arranged it
that they divided all their stock into two parts, or exact duplicates,
half of which they hid away, while the other half was exposed for sale.
While at dinner the Prince spoke much of magic, and professed to be
able to produce such a delirium in people’s minds that they would act
like lunatics. “Thus, for instance,” he said, pointing casually out of
the window, “you see all those women. I can drive them mad at once.”
Whereupon one who was present wagered a handsome carriage and four
horses that the Prince could not do it. The latter smiled, waved his
hand, and uttered a spell, when lo! all at once the market-women began,
_bacchantium more_--like raging Bacchantæ--to attack their crockery
with sticks and stools, and hurl it about, and dash it to pieces.
The one who had betted the chariot protested that it was a trick
arranged beforehand. The Prince replied, “Well, the pots are all
broken. If I can mend them again by a spell, wilt thou then believe?”
The other said, “Most certainly.” Then the Prince waved his wand and
said, “It is done. Let us go down into the courtyard and see.” And when
there, sure enough they found the pots all whole again--at least they
discovered others exactly like them in their places.
The legend continued that the Prince, though he kept the carriage and
horses as a trophy, liberally paid for them. The author of the _Tres
Centuriæ_, who does not record the secret of the little arrangement,
declares that he does not know whether it was all done by a fraud
or by magic. If it was the latter, I regret that the incantation by
which broken crockery is mended is now lost. The most powerful spell
known to me is _Recipe Gummæ Mastichæ duæ unciæ cum Spirito Vini
fiat mixtio_--that is, mastic cement. It is generally combined with
sturgeon’s bladder glue.
This cement answers very well for glass. One of the old recipes,
which was very good indeed, is thus given by JOHANNES WALLBURGER
(1760):--“Take finely cut and a little powdered sturgeon’s bladder”
(still sold by all chemists), “soften it all night in spirits, add to
this a little clean and powdered mastic, boil it a little in a brass
pan. Should it become too thick, add a little spirits.” This may be
also used for many other purposes.
A strong but coarser adhesive, especially for crockery and stone, can
be made as follows:--Take old and hard goat’s milk cheese, and warm it
in hot water till it forms, by pounding, a mass like turpentine. Add to
this, while grinding, finely pulverised quicklime and the well-shaken
white of eggs.
I do not hesitate to give a variety of such recipes, because in every
one the artist will find valuable suggestions for other purposes than
simply glueing broken articles together. This latter is a valuable
“filler” for many purposes. Glue was formerly made into a strong
cement by boiling it for a time in water, but before it had become
incorporated with the water, the latter was poured off and strong
spirits substituted and stirred well in.
A very popular old cement for crockery, of which there were several
variations, was made by mixing glue, turpentine, ox-gall, the juice
of garlic, and sturgeon-bladder, tragacanth, and mastic. All of this
singularly smelling mixture was put into a pan and boiled in strong
spirits, such as whisky, then kneaded on a board under a roller, again
boiled with more spirits, yet again rolled, and this was repeated a
third time, and then cooled till it could be cut into cakes. When these
were to be used they were again steeped in spirits. But with this
cement, glass or metal could be most firmly attached to wood. I confess
that I have never tried it, but it was evidently a very strong cement.
Another of these somewhat complicated recipes for crockery, glass,
and porcelain, which I find in the _Tausandkünstler_, 1782, is
as follows:--Half an ounce of finely cut sturgeon’s bladder, two
teaspoonfuls of alabaster powder or gypsum, quarter of an ounce of
tragacanth, one teaspoonful of silberglatt, two of powdered mastic,
two of frankincense, two of gum-arabic, one of Marienglas, one
tablespoonful of spirits of wine, one of beer-vinegar. Boil it and
stir, and apply. Any drops sticking to the mended article may be
removed with vinegar. When it is to be used again revive it by heating,
adding spirits of wine and beer-vinegar. The gum-frankincense is here
worth noting.
A common cement for mending broken glass or china is prepared as
follows:--To two parts of gum-shellac add one of turpentine; boil them
over a slow fire, and form the mass into small cakes before it dries.
To use it, warm with a lamp. To mend ivory or wood, take a cake and let
it dissolve in spirits of wine.
A very strong cement is made as follows:--Take one ounce of finely
powdered mastic dissolved in six of spirits of wine and two ounces of
shredded sturgeon’s bladder dissolved in two ounces common spirits; add
one half ounce of _gum-ammoniac_ as it hardens; warm it when it is to
be used. This is as strong a cement as can be made.
Defects, cracks, and repairs in porcelain, &c., may often be concealed
as follows:--Paint the spot with silicate of soda, not too much
thinned, and dust it over before it dries with bronze powder. This will
set so hard that it may be polished with an agate burnisher.
It is also possible that many of my readers have heard of _gesso
painting_, an art perfected by Mr. WALTER CRANE. This consists of
painting with plaster of Paris in solution, with the point of a brush,
depositing the soft paste in relief. The same principle is applicable
to painting in silicate and whiting on glass surfaces. By means of it
decoration can be given to any glass bottle or other object.
LIME enters into the composition of many cements, the simplest being
the mortar formed by its admixture with water. But the quality of
this is very much determined by that of the lime. The _chunam_ of
India, which resembles white marble or a fine white stone, is made of
sea-shells burned to lime. A wonderfully hard, fine, white cement used
by the Romans for their best mosaic-work, and which set with great
rapidity, was made of shell-lime with the white of eggs. I have found
the same composition worthless when made with inferior stone-lime.
A good cheap cement for porcelain and glass is combined as follows:--
Starch or wheat flour 8
Glue 4
Purified chalk 12
Turpentine 4
Spirits of wine 24
Water 24
Pour a part of the spirits and water mixed on the flour and chalk,
add the glue, boil it down till the latter dissolves, and stir the
turpentine into the whole. This can be used to make artificial wood
with shavings or sawdust.
A very good cement for porcelain, and one which is colourless, is made
by cutting the finest clear gelatine into bits, and dissolving it in
vinegar of 50°, stirring it in a porcelain vessel until well mixed.
When cold it will harden, but softens under the influence of heat,
when it may be applied to the broken edges of the porcelain, which are
to be pressed together. It will be perfectly hard within twenty-four
hours. It is to be observed that the art of keeping such joined pieces
together is the most difficult problem in mending. This cement is
widely applicable to many objects, and also admits of considerable
modification and additions, like all cements. As it is colourless, it
may be combined with ivory dust, or white powders of baryta, magnesia,
whiting, &c., to form artificial ivory with glycerine. With sturgeon’s
bladder it makes a still stronger cement.
LEHNER observes that glue has the property, when combined with acid
chrome salt (_sauren chromsalzen_), of losing its solubility when
exposed to the light, so that it can be used as a cement for broken
porcelain and glass. If the juncture is to be invisible, take the
purest white gelatine; otherwise the cheaper gilder’s glue will answer.
To prepare the chrome glue, dissolve the gelatine or the glue in
boiling water, then add the solution of double chromic acid alkali, or
the red chrome alkali of commerce, stir it well up, and put it into tin
boxes.
The formula is:--
Gelatine or gilders’ glue 5-10
Water 90
Red chrome alkali 1-2
Dissolved in water 10
To use, warm the cement, apply it to the broken glass, which must then
be exposed for several hours to the sunshine.
Cracked bottles are mended by a very ingenious process, described by
LEHNER. The bottle is corked, but not tightly, and then exposed to
heat about 100° centigrade. Then the cork is driven in tightly, which
causes an expansion of the cracks, which are at once filled by means
of a finely pointed brush with the silicate. Removed to a cooler place
the glass contracts on the as yet fluid silicate, and the fractures are
mended.
* * * * *
A VERY STRONG, CLEAN CEMENT FOR PORCELAIN OR GLASS is made as follows:--
Well-cleaned glass powder 10
” fluor spar powder 20
Silicate of soda solution 60
This must be very quickly stirred and applied. This is one of the
_hardest_ and best cements, and it resists heat and other influences
so well that when very carefully amalgamated it may be applied to the
manufacture of many useful articles. The same may be made with the
substitution of white pipeclay for fluor spar, or with the addition of
the same in somewhat larger proportion. Pipeclay or any good clay can
also be combined with glycerine to prevent its drying. With gelatine
and a _little_ glycerine it will harden and not crack.
This requires careful amalgamation and rapid work.
To prepare very fine glass-powder for this cement, heat any glass till
red-hot, then drop it into cold water. It may then be reduced in a
mortar to an impalpable powder.
Earthenware tubes or pipes which are to be exposed to intense heat may
be luted or joined with the following cement:--
Peroxide of manganese 80
White oxide of zinc 100
Silicate of soda 20
“This does _not melt_, save at a very high temperature; and when
melted it forms a glassy substance, which holds with extreme tenacity”
(LEHNER).
To prepare _caseine_ cement for crockery or marble, it may be observed
that we should always take _fresh_ white cheese and macerate or knead
it thoroughly till only pure CASEINE remains. By adding to this
one-third of powdered quicklime and blending the two ingredients
very thoroughly we get a very strong glue. An admixture of 10 parts
silicate of soda also forms a powerful cement.
The following for tile-work and common brick-crockery, or terra-cotta
or porcelain, is very highly commended by LEHNER, who says that
anything mended with it will sooner break in another place than where
it is cemented:--
Slacked lime 10
Borax 10
Litharge 5
The cement is mixed with water, and the tile or crockery, &c., heated
just before being mended.
I cannot insist too strongly on this--that no one is to expect that by
simply taking recipes, as written, compounding and applying them, there
will be a successful result at the first trial. We must always have the
best material, often fresh, and generally attempt the application more
than once. _Perseverando vinces_--“By perseverance you will conquer.”
Not only must the _quality_ of the ingredients used be of the best, but
the composition be made exactly in the order in which they are given.
The same substances often give very different results, simply because
the order of combination in the two was different.
TO REPAIR PAVEMENTS:--
Calcined lime 10
Purified chalk 100
Silicate of soda 25
This hardens slowly. It can, when mixed with small sharp-edged
fragments of broken stone, be used to form pavements, or as a bed for
mosaics. For the same purposes, or for cementing marble slabs, a cement
known as that of BÖTTGER may be used. It is made thus:--
Purified chalk 100
Thick solution silicate of soda 25
This becomes (LEHNER) in a few hours so hard that it can be polished.
It is the principal, and almost the only, cement used by M.
RIS-PACQUOT, or commended in his work on mending crockery. It admits
of a great variety of modifications. It is very superior as a bed for
mosaics of all kinds. It forms, like the preceding, also a good bed for
scagliola and ceresa.[1] I would here say of the latter, that I could
wish to see it more generally used for mural or wall ornament, since
any one who can paint a face or decoration boldly and largely in oil
or water colours will find it very easy. It admits of rapid execution,
and is striking from its brilliancy. Everything in it depends on
having a good bed to which it can easily adhere. I may here observe
that beds like these which set hard and _fine_ are also adapted to
fresco-painting, in which the difficulty is to select colours which,
when absorbed and dried, do not fade. Most paints made from mineral
substances combine with silicate of soda.
I may here remark that a curious and easy art, very little known,
consists of carving or cutting low reliefs on tiles or terra-cotta or
brick-like ware, which, when outlined or in relief, can be glazed in
colour with silicate of soda; also with many other cements.
A common and good CEMENT FOR PORCELAIN OR GLASS is made as follows:--
Calcined gypsum or plaster of Paris 50
Calcined lime 10
White of egg 20
This must be quickly mingled and rapidly used, as it sets very rapidly
and becomes extremely hard. It makes an admirable bed for mosaics or
ceresa.
When plaster of Paris is simply combined with burnt alum in water, the
objects mended with it require several weeks to set or adhere. Gypsum
combined with gum alone holds firmly, but does not resist water (vide
_General Recipes_).
CEMENTS FOR LUTING or closing chemical apparatus:--
Dried clay 10
Linseed-oil 1
This endures heat to boiling-point of quicksilver.
A more resistant fireproof is as follows:--
Manganese 10
Grey oxide of zinc 20
Clay 40
Linseed-oil varnish 7
Of the oil only so much is needed as to combine the mass to a paste.
A LUTING for very high temperatures:--
Clay 100
Glass powder 2
Another CEMENT:--
Clay 100
Chalk 2
Boracic acid 3
LEHNER has in his work on Cements many valuable suggestions as to
mending porcelain. _Firstly_, that in such mending, the adhesive be
applied with care, in as even and as thin a coat as possible; to
which I would add, that the unskilful amateur is apt to daub it on
irregularly and carelessly, with the impression that the more cement
there is the better it will stick, which is just so far wrong that
every superfluous grain is just so much of an impediment to good
drying or adhesion. Again, the inexpert daubs it on with a stick or
“anything,” when a fine-pointed brush or hair-pencil should be used.
BROKEN CHINA WHICH IS TO BE MENDED should be carefully covered away
so as to protect it from dust, which is hard to clean off. Beware of
fitting the pieces together again and again, as is often done.
If the broken china was used to contain milk or soup, &c., it should
be laid in lye to dissolve all the fatty substance, and then be washed
with clear water. Painted porcelain cannot, however, be laid in lye,
which would ruin all the colours; in this case wipe them clean with
dilute acid.
The great difficulty in mending is to bring the pieces together and
keep them so till the adhesive dries. LEHNER recommends that when
objects are small and costly, a mould of gypsum be constructed round
them. In most cases putty or wax is far more manageable. As before
remarked, indiarubber bands are chiefly to be relied on; even if not
capable of holding permanently, they aid greatly in tying with cord.
In the Manual of F. GOUPIL, rewritten by FREDERICK DILLAYE, the
following method of restoring broken vases, &c., is commended:--
“Form a solid mass of clay in the form of the original object. Then
place on it, one by one, the fragments in their place, keeping the clay
moist. When this is done, paste over the exterior strips of paper, in
sufficient quantity to hold the whole firmly together. Then remove
the moist clay, and paste strong slips of paper” (or thin parchment)
“over the interior so as to hold the whole. Then” (when dry) “carefully
moisten and remove the outer coating.”